High performance humidity sensing properties of indium tin oxide (ITO) thin films by sol-gel spin coating method

The tin doped indium oxide (ITO) thin films prepared by sol-gel spin coating method with In(NO3)3H(2)O and SnCl4 center dot 5H(2)O as indium and tin sources respectively is presented. The as deposited samples were annealed at 500 A degrees C for 2 h in order to improve the crystallinity. The structural, morphological and optical properties of the films were analysed by using X-ray diffraction, scanning electron microscope (SEM), UV-Vis transmission spectra and photoluminescence, spectra analysis. The SEM images ensure the uniform and smooth surface of the as prepared and annealed film. The optical transmittance of more than 85 % has been observed in the UV-Vis region with a band gap of 3.91 and 3.73 eV for the as prepared and annealed films of ITO respectively. The PL spectra reveal that the optical properties were significantly improved due to the annealing effect. The annealed film shows high sensitivity for humidity approximately two order changes in the resistance and the sensitivity increases for different relative humidity from 10 to 90 % due to the physisorption between the water molecules and the surface of the thin films.